Adriana Echazú 1 , 2 , * , Daniela Bonanno 3 , Marisa Juarez 1 , 4 , Silvana P. Cajal 1 , Viviana Heredia 5 , Silvia Caropresi 5 , Ruben O. Cimino 1 , Nicolas Caro 1 , Paola A. Vargas 1 , Gladys Paredes 5 , Alejandro J. Krolewiecki 1 , 2
30 September 2015
Soil-transmitted helminth (STH) infections are a public health problem in resource-limited settings worldwide. Chronic STH infection impairs optimum learning and productivity, contributing to the perpetuation of the poverty-disease cycle. Regular massive drug administration (MDA) is the cardinal recommendation for its control; along with water, sanitation and hygiene (WASH) interventions. The impact of joint WASH interventions on STH infections has been reported; studies on the independent effect of WASH components are needed to contribute with the improvement of current recommendations for the control of STH. The aim of this study is to assess the association of lacking access to water and sanitation with STH infections, taking into account the differences in route of infection among species and the availability of adequate water and sanitation at home.
Cross-sectional study, conducted in Salta province, Argentina. During a deworming program that enrolled 6957 individuals; 771 were randomly selected for stool/serum sampling for parasitological and serological diagnosis of STH. Bivariate stratified analysis was performed to explore significant correlations between risk factors and STH infections grouped by mechanism of entry as skin-penetrators (hookworms and Strongyloides stercoralis) vs. orally-ingested ( Ascaris lumbricoides and Trichuris trichiura). After controlling for potential confounders, unimproved sanitation was significantly associated with increased odds of infection of skin-penetrators (adjusted odds ratio [aOR] = 3.9; 95% CI: 2.6–5.9). Unimproved drinking water was significantly associated with increased odds of infection of orally-ingested (aOR = 2.2; 95% CI: 1.3–3.7).
Lack of safe water and proper sanitation pose a risk of STH infections that is distinct according to the route of entry to the human host used by each of the STH species. Interventions aimed to improve water and sanitation access should be highlighted in the recommendations for the control of STH.
Soil-transmitted helminths (STH) are a group of parasitic human infections of great public health relevance due to their high prevalence and potentially severe morbidity in case of heavy infection intensity, especially in poor settings. Common species of STH include Ascaris lumbricoides, Trichuris trichiura, Hookworm ( Ancylostoma duodenale and Necator americanus) and Strongyloides stercoralis. Their life cycle includes an obligatory passage on soil, where they mature becoming capable of transmitting the infection to a new host. Two infective routes can be distinguished according to the species, oral ingestion of eggs versus skin penetration of larvae from fecally contaminated soil. Inadequate sanitation and unsafe water supply were described as risk factors for STH infections; however more data on this relationship is needed. The main strategy for STH control is the regular deworming, through mass drug administration. Interventions on water, sanitation and hygiene (WASH) and health education are also important to sustain the benefits of anthelmintic therapy. The present study reports an association between poor sanitation and water access and STH infections selective to the parasite route of entry. This finding could contribute to the design of specific and rational recommendations to reduce soil-transmitted helminths transmission.